Multilayer structures as stable hole-injecting electrodes for use in high efficiency organic electronic devices

ABSTRACT

Multilayer anode structures ( 104 ) for electronic devices ( 100 ) such as polymer light-emitting diodes are described. The multilayer anodes include a high conductivity organic layer ( 114 ) adjacent to the photoactive layer ( 102 ) and a low conductivity organic layer ( 112 ) between the high conductivity organic layer and the anode&#39;s electrical connection layer ( 110 ). This anode structure provides polymer light emitting diodes which exhibit high brightness, high efficiency and long operating lifetime. The multilayer anode structure of this invention provides sufficiently high resistivity to avoid cross-talk in passively addressed pixellated polymer emissive displays; the multilayer anode structure of this invention simultaneously provides long lifetime for pixellated polymer emissive displays.

FIELD OF THE INVENTION

[0001] This invention relates to organic electronic devices. Moreparticularly it concerns multilayer hole-injecting electrodes (anodes)for electronic devices.

DESCRIPTION OF PRIOR ART

[0002] Organic electronic devices, such as light emitting devices,photodetecting devices and photovoltaic cells, may be formed of a thinlayer of electroactive organic material sandwiched between twoelectrical contact layers. Electroactive organic materials are organicmaterials exhibiting electroluminescence, photosensitivity, charge (holeor electron) transport and/or injection, electrical conductivity, and/orexciton blocking. The material may be semiconductive. At least one ofthe electrical contact layers is transparent to light so that light canpass through the electrical contact layer to or from the electroactiveorganic material layer. Other devices with similar structures includephotoconductive cells, photoresistive cells, photodiodes, photoswitches,transistors, capacitors, resistors, chemoresistive sensors (gas/vaporsensitive electronic noses, chemical and biosensors), writing sensors,and electrochromic devices (smart windows).

[0003] Light-emitting diodes (LEDs) fabricated with conjugated organicpolymer layers as their emissive elements have attracted attention dueto their potential for use in display technology [J. H. Burroughs, D. D.C. Bradley, A. R. Brown, R. N. Marks, K. Mackay, R. H. Friend, P. L.Burns, and A. B. Holmes, Nature 347, 539 (1990); D. Braun and A. J.Heeger, Appl. Phys. Lett. 58, 1982 (1991)]. Patents covering polymerLEDs include the following: R. H. Friend, J. H. Burroughs and D. D.Bradley, U.S. Pat. No. 5,247,190; A. J. Heeger and D. Braun, U.S. Pat.Nos. 5,408,109 and 5,869,350. These references as well as all additionalarticles, patents and patent applications referenced herein areincorporated by reference.

[0004] In their most elementary form, these diodes employ a layer ofconjugated organic polymer bounded on one side by a hole-injectingelectrode (anode) and on the other by an electron-injecting electrode(cathode), one of which is transparent to the light produced in theconjugated polymer layer when a potential is applied across it.

[0005] In many applications, especially in displays, arrays of thesediodes are assembled. In these applications, there is typically a unitbody of active polymer and the electrodes are patterned to provide thedesired plurality of pixels in the array. With arrays based on a unitbody of active polymer and patterned electrodes there is a need tominimize interference or “cross talk” among adjacent pixels. This needhas also been addressed by varying the nature of the contacts betweenthe active polymer body and the electrodes.

[0006] The desire to improve operating life and efficiency is oftenseemingly at cross purposes with the desire to minimize cross talk. Highefficiency and long operating life are promoted by the use of highconductivity contacts with the active material layer. Cross talk isminimized when the resistance between adjacent pixels is high.Structures which favor high conductivity and thus high efficiency andlong operating life are contrary to the conditions preferred for lowcross talk.

[0007] In U.S. Pat. No. 5,723,873 it is disclosed that it isadvantageous to place a layer of conductive polyaniline (PANI) betweenthe hole-injecting electrode and the layer of active material toincrease diode efficiency and to lower the diode's turn on voltage.

[0008] Hole-injecting anodes which include conductive polyaniline canprovide sufficiently high resistivity to avoid the disadvantage of crosstalk in pixellated polymer emissive displays. However, the lifetime ofsuch high resistivity polyaniline devices is not sufficient for manycommercial applications. Moreover, devices fabricated withpolyaniline-layer-containing anodes require high operating voltages.

[0009] Additional developments using a layer of polyaniline or blendscomprising polyaniline, directly between the ITO and the light-emittingpolymer layer, C. Zhang, G. Yu and Y. Cao [U.S. Pat. No. 5,798,170]demonstrated polymer LEDs with long operating lifetimes.

[0010] Despite the advantages of the polymer LED's described in U.S.Pat. No. 5,798,170, the low electrical resistivity typical ofpolyaniline inhibits the use of polyaniline in pixellated displays. Foruse in pixellated displays, the polyaniline layer should have a highelectrical sheet resistance, otherwise lateral conduction causescross-talk between neighboring pixels. The resulting interpixel currentleakage significantly reduces the power efficiency and limits both theresolution and the clarity of the display.

[0011] Making the polyaniline sheet resistance higher by reducing thefilm thickness is not a good option since thinner films give lowermanufacturing yield caused by the formation of electrical shorts. Thisis demonstrated clearly in FIG. 1, which shows the fraction of “leaky”pixels in a 96×64 array vs thickness of the polyaniline polyblend layer.Thus, to avoid shorts, it is necessary to use a relatively thickpolyaniline layer with thickness ˜200 nm.

[0012] In polymer emissive displays, good operating lifetimes andrelatively lower operating voltages have been demonstrated through theuse of a layer of poly(ethylenedioxythiophene) (PEDT) between anindium/tin-oxide (ITO) anode layer and the emissive polymer layer. PEDT,as typically prepared, has intrinsically low electrical resistivity.However, for use in pixellated displays, the PEDT layer needs to have ahigh electrical sheet resistance, otherwise lateral conduction causescross-talk between neighboring pixels, and the resulting inter-pixelcurrent leakage significantly reduces the power efficiency and limitsboth the resolution and the clarity of the display.

[0013] Thus, there is a need for anode structures for light emittingdevices which avoid inter-pixel cross-talk, and which exhibit the lowoperating voltages and the extended operating lifetimes consistent withthe requirements of commercial applications.

SUMMARY OF THE INVENTION

[0014] This invention relates generally a multilayer anode structureuseful for organic electronic devices, such as diodes and pixellateddisplays.

[0015] The multilayer anode includes a first layer comprising a highconductivity contact layer having a first layer conductivity, a secondlayer in contact with the first layer, said second layer comprising aconductive organic material having a second layer conductivity, and athird layer in contact with the second layer, said third layercomprising a conductive organic polymer having a third layerconductivity greater than the second layer conductivity and less thanthe first layer conductivity.

[0016] The multilayer structure provides sufficiently high resistivityto avoid cross-talk in passively-addressed pixellated polymer emissivedisplays; the multilayer anode structure of this inventionsimultaneously provides the low operating voltages and the longoperating lifetime required for pixellated polymer emissive displays incommercial applications.

[0017] This invention additionally provides an improved configurationfor electronic devices such as pixellated polymer emissive displays.This configuration leads to high efficiency, long operating life PED'swhile at the same time avoids excessive cross talk. This inventionrelates generally to the use of the multilayer anode structure in suchdevices. Thus, in one aspect this invention provides an improved polymeremissive diode. This improved diode is made up of an active emissivepolymer layer having a first side in contact with a cathode and a secondside in contact with a transparent anode. The improvement involves amultilayer transparent anode itself made up of a high conductivitytransparent first contact layer, a transparent second layer in contactwith the first contact layer and a third layer in contact with thesecond layer and the active emissive polymer layer. The second layercontains conjugated conductive organic polymer blend and has a highresistance. The third layer is thin and contains a conductive organicpolymer having a lower resistance than the material of the second layer.

[0018] While the multilayer electrode of the invention is useful innon-pixelated as well as pixelated electronic devices, the use of theseimproved multilayer anode structures is particularly advantageous when aplurality of diodes are arranged into an array as occurs in pixellatedemissive displays as the anode structure leads to very low levels ofcross talk while at the same time providing long life and highefficiency as compared to arrays described heretofore.

[0019] In this aspect this invention provides an improved array ofpolymer emissive diodes. This improved diode array is made up of anactive emissive polymer layer having a first side in contact with apatterned cathode and a second side in contact with a patternedtransparent anode, the patterning of the anode and cathode defining anarray of emissive diodes, the improvement comprising a multilayertransparent anode including a first layer comprising a patterned highconductivity transparent contact layer, a nonpatterned transparentsecond layer in contact with said first layer, the second layercomprising a blend of conjugated conductive organic polymer and having ahigher resistance (lower conductivity) and a nonpatterned transparentthird layer in contact with the second layer and with the activeemissive polymer layer, the third layer comprising a conductive organicpolymer and having a lower resistance (higher conductivity) than thesecond layer.

[0020] As used herein, the term “organic electroactive material” refersto any organic material that exhibits the specified electroactivity,such as electroluminescence, photosensitivity, charge transport and/orcharge injection, electrical conductivity and exciton blocking. The term“solution-processed organic electroactive material” refers to anyorganic electroactive material that has been incorporated in a suitablesolvent during layer formation in electronic device assembly. The term“charge” when used to refer to charge injection/transport refers to oneor both of hole and electron transport/injection, depending upon thecontext. The term “photoactive” organic material refers to any organicmaterial that exhibits the electroactivity of electroluminescence and/orphotosensitivity. The terms “conductivity” and “bulk conductivity” areused interchangeably, the value of which is provided in the unit ofSiemens per centimeter (S/cm). In addition, the terms “surfaceresistivity” and “sheet resistance” are used interchangeably to refer tothe resistance value that is a function of sheet thickness for a givenmaterial, the value of which is provided in the unit of ohm per square(ohm/sq). Also, the terms “bulk resistivity” and “electricalresistivity” are used interchangeably to refer to the resistivity thatis a basic property of a specific materials (i.e., does not change withthe dimension of the substance), the value of which provided in the unitof ohm-centimeter (ohm-cm). Electrical resistivity value is the inversevalue of conductivity.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] This invention will be described with˜reference being made to thedrawings. In these drawings,

[0022]FIG. 1 is a graph referenced in the Background which shows thefraction of “leaky” pixels (in a 96 by 64 array) vs thickness of apolyaniline layer.

[0023]FIG. 2A is a not-to-scale cross-sectional view of a pixel anorganic electronic device of the invention containing a photoactivelayer.

[0024]FIG. 2B is an enlarged cross section of the pixel of FIG. 2Afocusing on the multilayer anode structure.

[0025]FIG. 2C is a schematic diagram of the architecture of apassively-addressed, pixellated, organic electronic device of theinvention containing a photoactive layer.

[0026]FIG. 3 is a graph which shows the stress-induced degradation ofthree devices, one with a polyaniline (emeraldine-salt) layer(PANI(ES)), one with a layer made with a blend of polyaniline withpolyacrylamide (PANI(ES)-PAM) and one with a layer ofpoly(ethylenedioxythiophene) (PEDT) layer at 70° C. Solid linesrepresent operating voltage and dashed lines represent light output.

[0027]FIG. 4 is a graph which shows the stress-induced degradation ofdevices having a PANI(ES)-PAM/PEDT double layer with different PEDTthickness at 70° C. Solid lines represent operating voltage and dashedlines represent light output.

[0028]FIG. 5 is a graph which shows the stress-induced degradation of aseries of devices having PANI(ES)-PAM/PEDT double layers with differentPANI(ES)-PAM blends at 80° C. Solid lines represent operating voltageand dashed lines represent light output.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0029] As best seen in FIGS. 2A, 2B, and 2C, an electronic device 100 ofthis invention comprises a layer of photoactive layer 102 between acathode 106 and a multilayer anode 104. Anode 104 includes a conductivefirst layer 110 having a first layer conductivity, a low conductivitysecond layer 112 having a second layer conductivity and a highconductivity third layer 114 having a third layer conductivity greaterthan the second layer conductivity and less than the first layerconductivity. Anode 104 and the overall diode structure can be carriedon a substrate 108.

[0030] Organic polymer-based diode 100 employs a relatively high workfunction anode; this high work function anode 104 serving to injectholes into the otherwise filled π-band of the semiconducting,luminescent polymer 102. Relatively low work function materials arepreferred as the cathode 106; this low work function cathode serving toinject electrons into the otherwise empty π*-band of the semiconducting,luminescent polymer 102. The holes injected at the anode and theelectrons injected at the cathode recombine radiatively within theactive layer and light is emitted. The criteria for suitable electrodesin the art are described in detail by I. D. Parker, J. Appl. Phys, 75,1656 (1994).

[0031] Device Configuration:

[0032] As best seen in FIG. 2C, each individual pixel of an organicelectronic device 100 includes an electron injecting (cathode) contact106 as one electrode on the front of a photo active organic material 102deposited on a multi layer anode 104 of the invention to serve as thesecond (transparent) electron-withdrawing (anode) electrode. Themultilayer anode (made of layers 110, 112 and 114) is deposited on asubstrate 108, which is partially coated with a first layer 110.Deposited on top of first layer 110 is the low conductivity second layer112 and the high conductivity third layer 114. Cathode 106 iselectrically connected to contact pads 80, and anode 110 is electricallyconnected to contact pads 82. The layers 102, 106, 108, 110, and 112 arethen isolated from the environment by a hermetic seal layer 114. Wherethe electronic device is a light-emitting device, upon application ofelectricity via contact pads 80, 82, which pads are outside of thehermetic seal 70, light is emitted from the device in the directionshown by arrow 90. Where the electronic device is a photodetector, lightis received by the deice in the direction opposite the arrow 90 (notshown).

[0033] This description of preferred embodiments is organized accordingto these various components. More specifically it contains the followingsections:

[0034] The Photoactive layer (102)

[0035] The Multilayer Anode (104)

[0036] The Conductive First Layer (110)

[0037] The Low Conductivity Second Layer (112)

[0038] The High Conductivity Third Layer (114)

[0039] The Cathode (106)

[0040] The Substrate (108)

[0041] Contact Pads (80, 90)

[0042] Optional Layers

[0043] Fabrication Techniques

[0044] The Photoactive Layer (102)

[0045] Depending upon the application of the electronic device, thephotoactive layer 102 can be a light-emitting layer that is activated byan applied voltage (such as in a light-emitting diode or light-emittingelectrochemical cell), a layer of material that responds to radiantenergy and generates a signal with or without an applied bias voltage(such as in a photodetector). Examples of photodetectors includephotoconductive cells, photoresistors, photoswitches, phototransistors,and phototubes, and photovoltaic cells, as these terms are describe inMarkus, John, Electronics and Nucleonics Dictionary, 470 and 476(McGraw-Hill, Inc. 1966).

[0046] Where the electronic device is a light-emitting device, thephotoactive layer 102 will emit light when sufficient bias voltage isapplied to the electrical contact layers. Suitable active light-emittingmaterials include organic molecular materials such asanthracene,butadienes, coumarin derivatives, acridine, and stilbene derivatives,see, for example, Tang, U.S. Pat. No. 4,356,429, Van Slyke et al., U.S.Pat. No. 4,539,507, the relevant portions of which are incorporatedherein by reference. Alternatively, such materials can be polymericmaterials such as those described in Friend et al. (U.S. Pat. No.5,247,190), Heeger et al. (U.S. Pat. No. 5,408,109), Nakano et al. (U.S.Pat. No. 5,317,169), the relevant portions of which are incorporatedherein by reference. The light-emitting materials may be dispersed in amatrix of another material, with and without additives, but preferablyform a layer alone. In preferred embodiments, the electroluminescentpolymer comprises at least one conjugated polymer or a co-polymer whichcontains segments of π-conjugated moieties. Conjugated polymers are wellknown in the art (see, e.g., Conjugated Polymers, J.-L. Bredas and R.Silbey edt., Kluwer Academic Press, Dordrecht, 1991). Representativeclasses of materials include, but are not limited to the following:

[0047] (i) poly(p-phenylene vinylene) and its derivatives substituted atvarious positions on the phenylene moiety;

[0048] (ii) poly(p-phenylene vinylene) and its derivatives substitutedat various positions on the vinylene moiety;

[0049] (iii) poly(arylene vinylene), where the arylene may be suchmoieties as naphthalene, anthracene, furylene, thienylene, oxadiazole,and the like, or one of the moieties with functionalized substituents atvarious positions;

[0050] (iv) derivatives of poly(arylene vinylene), where the arylene maybe as in (iii) above, substituted at various positions on the arylenemoiety;

[0051] (v) derivatives of poly(arylene vinylene), where the arylene maybe as in (iii) above, substituted at various positions on the vinylenemoiety;

[0052] (vi) co-polymers of arylene vinylene oligomers withnon-conjugated oligomers, and derivatives of such polymers substitutedat various positions on the arylene moieties, derivatives of suchpolymers substituted at various positions on the vinylene moieties, andderivatives of such polymers substituted at various positions on thearylene and the vinylene moieties;

[0053] (vii) poly(p-phenylene) and its derivatives substituted atvarious positions on the phenylene moiety, including ladder polymerderivatives such as poly(9,9-dialkyl fluorene) and the like;

[0054] (viii) poly(arylenes) and their derivatives substituted atvarious positions on the arylene moiety;

[0055] (ix) co-polymers of oligoarylenes with non-conjugated oligomers,and derivatives of such polymers substituted at various positions on thearylene moieties;

[0056] (x) polyquinoline and its derivatives;

[0057] (xi) co-polymers of polyquinoline with p-phenylene and moietieshaving solubilizing function;

[0058] (xii) rigid rod polymers such aspoly(p-phenylene-2,6-benzobisthiazole),poly(p-phenylene-2,6-benzobisoxazole),poly(p-phenylene-2,6-benzimidazole), and their derivatives; and thelike.

[0059] More specifically, the active materials may include but are notlimited to poly(phenylenevinylene), PPV, and alkoxy derivatives of PPV,such as for example,poly(2-methoxy-5-(2′-ethyl-hexyloxy)-p-phenylenevinylene) or “MEH- PPV”(U.S. Pat. No. 5,189,136). BCHA-PPV is also an attractive activematerial. (C. Zhang, et al, J. Electron. Mater., 22, 413 (1993)). PPPVis also suitable. (C. Zhang et al, Synth. Met., 62, 35 (1994) andreferences therein.) Luminescent conjugated polymer which are soluble incommon organic solvents are preferred since they enable relativelysimple device fabrication [A. Heeger and D. Braun, U.S. Pat. Nos.5,408,109 and 5,869,350].

[0060] Even more preferred active light-emitting polymers and copolymersare the soluble PPV materials described in H. Becker et al., Adv. Mater.12, 42 (2000) and referred to herein as C-PPV's. Blends of these andother semi-conducting polymers and copolymers which exhibitelectroluminescence can be used. Where the electronic device 100 is aphotodetector, the photoactive layer 102 responds to radiant energy andproduces a signal either with or without a biased voltage. Materialsthat respond to radiant energy and is capable of generating a signalwith a biased voltage (such as in the case of a photoconductive cells,photoresistors, photoswitches, phototransistors, phototubes) include,for example, many conjugated polymers and electroluminescent materials.Materials that respond to radiant energy and are capable of generating asignal without a biased voltage (such as in the case of aphotoconductive cell or a photovoltaic cell) include materials thatchemically react to light and thereby generate a signal. Suchlight-sensitive chemically reactive materials include for example, manyconjugated polymers and electro- and photo-luminescent materials.Specific examples include, but are not limited to, MEH-PPV (“Optocouplermade from semiconducting polymers”, G. Yu, K. Pakbaz, and A. J. Heeger,Journal of Electronic Materials, Vol. 23, pp 925-928 (1994); and MEH-PPVComposites with CN-PPV (“Efficient Photodiodes from InterpenetratingPolymer Networks”, J. J. M. Halls et al. (Cambridge group) Nature Vol.376, pp. 498-500, 1995). The electroactive organic materials can betailored to provide emission at various wavelengths.

[0061] In some embodiments, the polymeric photoactive material ororganic molecular photoactive material is present in the photoactivelayer 102 in admixture from 0% to 75% (w, basis overall mixture) ofcarrier organic material (polymeric or organic molecular). The criteriafor the selection of the carrier organic material are as follows. Thematerial should allow for the formation of mechanically coherent films,at low concentrations, and remain stable in solvents that are capable ofdispersing, or dissolving the conjugated polymers for forming the film.Low concentrations of carrier materials are preferred in order tominimize processing difficulties, i.e., excessively high viscosity orthe formation of gross in homogeneities; however the concentration ofthe carrier should be high enough to allow for formation of coherentstructures. Where the carrier is a polymeric material, preferred carrierpolymers are high molecular weight (M.W.>100,000) flexible chainpolymers, such as polyethylene, isotactic polypropylene, polyethyleneoxide, polystyrene, and the like. Under appropriate conditions, whichcan be readily determined by those skilled in the art, thesemacromolecular materials enable the formation of coherent structuresfrom a wide variety of liquids, including water, acids, and numerouspolar and non-polar organic solvents. Films or sheets manufactured usingthese carrier polymers have sufficient mechanical strength at polymerconcentrations as low as 1%, even as low as 0.1%, by volume to enablethe coating and subsequent processing as desired. Examples of suchcoherent structures are those comprised of poly(vinyl alcohol),poly(ethylene oxide), poly-para (phenylene terephthalate),poly-para-benzamide, etc., and other suitable polymers. On the otherhand, if the blending of the final polymer cannot proceed in a polarenvironment, non-polar carrier structures are selected, such as thosecontaining polyethylene, polypropylene, poly(butadiene), and the like.

[0062] Typical film thicknesses of the photoactive layers range from afew hundred Ångstrom units (200 Å) to several thousand Angstrom units(10,000 Å) (1 Ångstrom unit=10⁻⁸ cm). Although the active filmthicknesses are not critical, device performance can typically beimproved by using thinner films. Preferred thickness are from 300 Å to5,000 Å.

[0063] The Multilayer Anode (104)

[0064] The multilayer anode (104) includes the conductive first layer(110), a low conductivity second layer (112) and a high conductivitythird layer (114).

[0065] The thickness of each layer 110, 112, 114 is determined by thedesired transparency and resistivity of such layer, such transparencyand resistivity factors are in turn dependent upon the composition ofthe layer.

[0066] In the device of the invention that contains a photoactive layer,one electrode is transparent to enable light emission from the device orlight reception by the device. Most commonly, the anode is thetransparent electrode, although the present invention can also be usedin an embodiment where the cathode is the transparent electrode.

[0067] As used herein, the term “transparent” is defined to mean“capable of transmitting at least about 25%, and preferably at leastabout 50%, of the amount of light of a particular wavelength ofinterest”. Thus a material is considered “transparent” even if itsability to transmit light varies as a function of wave length but doesmeet the 25% or 50% criteria at a given wavelength of interest. As isknown to those working in the field of thin films, one can achieveconsiderable degrees of transparency with metals if the layers are thinenough, for example in the case of silver and gold below about 300 Å,and especially from about 20 Å to about 250 Å with silver having arelatively colorless (uniform) transmittance and gold tending to favorthe transmission of yellow to red wavelengths. Similarly, for materialssuch as ITO, PANI and PEDT, transparency can be achieved with a layerranging from 100 Å to 10,000 Å.

[0068] In addition to the desired transparency, the composition oflayers in the multilayer anode 104 should also be chosen so that thethird layer conductivity is less than the first layer conductivity andmore than the second layer conductivity. Therefore, the choice ofmaterial for one layer of the multilayer anode depends upon thecomposition of the other layers in the anode and the correspondingconductivities of such other layers. Other factors in determiningcomposition are described below in sections relating to the specificlayers.

[0069] The Conductive First Layer (110)

[0070] The conductive first layer has low resistance: preferably lessthan 300 ohms/square and more preferably less than 100 ohms/square.

[0071] The conductive first layer (110) of the composite anode (104)provides electrical contact with an external electrical source (notshown) and is a conductive layer made of a high work function material,most typically an inorganic material with a work function above about4.5 eV. The conductive first layer 110 is preferably made of materialscontaining a metal, mixed metal, alloy, metal oxide or mixed-metaloxide. Suitable metals include the Group 11 metals, the metals in Groups4, 5, and 6, and the Group 8-10 transition metals. If the anode 104 isto be light-transmitting, mixed-metal oxides of Groups 12, 13 and 14metals, such as indium-tin-oxide, are generally used. The IUPACnumbering system is used throughout, where the groups from the PeriodicTable are numbered from left to right as 1-18 (CRC Handbook of Chemistryand Physics, 81^(st) Edition, 2000). The first layer 110 may alsocomprise an organic material such as polyaniline as described in“Flexible light-emitting diodes made from soluble conducting polymer,”Nature vol. 357, pp 477-479 (Jun. 11, 1992).

[0072] Typical inorganic materials which serve as anodes include metalssuch as aluminum, silver, platinum, gold, palladium, tungsten, indium,copper, iron, nickel, zinc, lead and the like; metal oxides such as leadoxide, tin oxide, indium/tin-oxide and the like; graphite; dopedinorganic semiconductors such as silicon, germanium, gallium arsenide,and the like. When metals such as aluminum, silver, platinum, gold,palladium, tungsten, indium, copper, iron, nickel, zinc, lead and thelike are used, the anode layer should be sufficiently thin to besemi-transparent. Metal oxides such as indium/tin-oxide are typically atleast semitransparent.

[0073] Where the anode is transparent, the conductive metal-metal oxidemixtures can be transparent as well at thicknesses up to as high as 2500Å in some cases. Preferably, the thicknesses of metal-metal oxide (ordielectric) layers is from about 25 to about 1200 Å when transparency isdesired.

[0074] The Low Conductivity Second Layer (112)

[0075] The second layer 112 should have sufficient high resistivity toprevent cross talk or current leakage from the multilayer anode andprovide sufficient hole injection/transport. The low conductivity secondlayer preferably has a bulk conductivity of from about 10⁻⁴ S/cm to10⁻¹¹ S/cm. More preferably, the second layer has a bulk conductivity offrom 10⁻⁵ S/m to 10⁻⁸ S/cm.

[0076] The second layer 112 may comprise polyaniline (PANI) or anequivalent conjugated conductive polymer such as polypyrole orpolythiophene, most commonly in a blend with one or more nonconductivepolymers. Polyaniline is particularly useful. Most commonly it is in theemeraldine salt (ES) form. Useful conductive polyanilines include thehomopolymer and derivatives usually as blends with bulk polymers (alsoknown as host polymers). Examples of PANI are those disclosed in U.S.Pat. No. 5,232,631.

[0077] In another embodiment, the second layer may include conductivematerials such as N,N′-diphenyl-N,N′-bis(3-methylphenyl)-[1,1′-biphenyl]-4,4′-diamine (TPD) andbis[4-(N,N-diethylamino)-2-methylphenyl](4-methylphenyl)methane (MPMP),and hole injection/transport polymers such as polyvinylcarbazole (PVK),(phenylmethyl)polysilane, poly(3,4-ethylenedioxythiophene) (PEDOT), andpolyaniline (PANI);electron and hole injection/transporting materialssuch as 4,4′-N,N′-dicarbazole biphenyl (BCP); or light-emittingmaterials with good electron and hole transport properties, such aschelated oxinoid compounds, such as tris(8-hydroxyquinolato)aluminum(Alq₃).

[0078] When the terms “polyaniline” or PANI are used herein, they areused generically to include substituted and unsubstituted materials, aswell as other equivalent conjugated conductive polymers such as thepolypyrroles, or the polythiophenes, for examplepoly(ethylenedioxythiophene) (“PEDT”) unless the context is clear thatonly the specific nonsubstituted form is intended. It is also used in amanner to include any accompanying dopants, particularly acidicmaterials used to render the polyaniline conductive.

[0079] In general, polyanilines are polymers and copolymers of film andfiber-forming molecular weight derived from the polymerization ofunsubstituted and substituted anilines of the Formula I:

[0080] wherein

[0081] n is an integer from 0 to 4;

[0082] m is an integer from 1 to 5 with the proviso that the sum of nand m is equal to 5; and

[0083] R is independently selected so as to be the same or different ateach occurrence and is selected from the group consisting of alkyl,alkenyl, alkoxy, cycloalkyl, cycloalkenyl, alkanoyl, alkythio, aryloxy,alkylthioalkyl, alkylaryl, arylalkyl, amino, alkylamino, dialkylamino,aryl, alkylsulfinyl, alkoxyalkyl, alkylsulfonyl, arylthio, arylsulfonyl,alkoxycarbonyl, arylsulfonyl, carboxylic acid, halogen, cyano, or alkylsubstituted with one or more sulfonic acid, carboxylic acid, halo,nitro, cyano or epoxy moieties; or carboxylic acid, halogen, nitro,cyano, or sulfonic acid moieties; or any two R groups together may forman alkylene or alkenylene chain completing a 3, 4, 5, 6 or 7-memberedaromatic or alicyclic ring, which ring may optionally include one ormore divalent nitrogen, sulfur or oxygen atoms. Without intending tolimit the scope of this invention, the size of the various R groupsranges from about 1 carbon (in the case of alkyl) through 2 or morecarbons up through about 20 carbons with the total of n Rs being fromabout 1 to about 40 carbons.

[0084] Illustrative of the polyanilines useful in the practice of thisinvention are those of the Formula II to V:

[0085] wherein:

[0086] n, m and R are as described above except that m is reduced by 1as a hydrogen is replaced with a covalent bond in the polymerization andthe sum of n plus m equals 4;

[0087] y is an integer equal to or greater than 0;

[0088] x is an integer equal to or greater than 1, with the proviso thatthe sum of x and y is greater than 1; and

[0089] z is an integer equal to or greater than 1.

[0090] The following listing of substituted and unsubstituted anilinesare illustrative of those which can be used to prepare polyanilinesuseful in the practice of this invention. Aniline 2,5-Dimethylanilineo-Toluidine 2,3-Dimethylaniline m-Toluidine 2,5-Dibutylanilineo-Ethylaniline 2,5-Dimethoxyaniline m-EthylanilineTetrahydronaphthylamine o-Ethoxyaniline o-Cyanoaniline m-Butylaniline2-Thiomethylaniline m-Hexylaniline 2,5-Dichloroaniline m-Octylaniline3-(n-Butanesulfonic acid) aniline 4-Bromoaniline 2-Bromoaniline3-Bromoaniline 2,4-Dimethoxyaniline 3-Acetamidoaniline 4-Mercaptoaniline4-Acetamidoaniline 4-Methylthioaniline 5-Chloro-2-methoxyaniline3-Phenoxyaniline 5-Chloro-2-ethoxyaniline 4-Phenoxyaniline

[0091] Illustrative of useful R groups are alkyl, such as methyl, ethyl,octyl, nonyl, tert-butyl, neopentyl, isopropyl, sec-butyl, dodecyl andthe like, alkenyl such as 1-propenyl, 1-butenyl, 1-pentenyl, 1-hexenyl,1-heptenyl, 1-octenyl and the like; alkoxy such as propoxy, butoxy,methoxy, isopropoxy, pentoxy, nonoxy, ethoxy, octoxy, and the like,cycloalkenyl such as cyclohexenyl, cyclopentenyl and the like; alkanoylsuch as butanoyl, pentanoyl, octanoyl; ethanoyl, propanoyl and the like;alkylsulfinyl, alkysulfonyl, alkylthio, arylsulfonyl, arylsulfinyl, andthe like, such as butylthio, neopentylthio, methylsulfinyl,benzylsulfinyl, phenylsulfinyl, propylthio, octylthio, nonylsulfonyl,octylsulfonyl, methylthio, isopropylthio, phenylsulfonyl,methylsulfonyl, nonylthio, phenylthio, ethylthio, benzylthio,phenethylthio, naphthylthio and the like; alkoxycarbonyl such asmethoxycarbonyl, ethoxycarbonyl, butoxycarbonyl and the like, cycloalkylsuch as cyclohexyl, cyclopentyl, cyclooctyl, cycloheptyl and the like;alkoxyalkyl such as methoxymethyl, ethoxymethyl, butoxymethyl,propoxyethyl, pentoxybutyl and the like; aryloxyalkyl and aryloxyarylsuch as phenoxyphenyl, phenoxymethylene and the like; and varioussubstituted alkyl and aryl groups such as 1-hydroxybutyl, 1-aminobutyl,1-hydroxylpropyl, 1-hydyroxypentyl, 1-hydroxyoctyl, 1-hydroxyethyl,2-nitroethyl, trifluoromethyl, 3,4-epoxybutyl, cyanomethyl,3-chloropropyl, 4-nitrophenyl, 3-cyanophenyl, and the like; sulfonicacid terminated alkyl and aryl groups and carboxylic acid terminatedalkyl and aryl groups such as ethylsulfonic acid, propylsulfonic acid,butylsulfonic acid, phenylsulfonic acid, and the correspondingcarboxylic acids.

[0092] Also illustrative of useful R groups are divalent moieties formedfrom any two R groups such as moieties of the formula:

[0093] wherein n* is an integer from about 3 to about 7, as for example—(CH₂)₋₄, —(CH₂)₋₃ and —(CH₂)₋₅, or such moieties which optionallyinclude heteroatoms of oxygen and sulfur such as —CH₂SCH₂— and—CH₂—O—CH₂—. Exemplary of other useful R groups are divalent alkenylenechains including 1 to about 3 conjugated double bond unsaturation suchas divalent 1,3-butadiene and like moieties.

[0094] Preferred for use in the practice of this invention arepolyanilines of the above Formulas II to V in which:

[0095] n is an integer from 0 to about 2;

[0096] m is an integer from 2 to 4, with the proviso that the sum of nand m is equal to 4;

[0097] R is alkyl or alkoxy having from 1 to about 12 carbon atoms,cyano, halogen, or alkyl substituted with carboxylic acid or sulfonicacid substituents;

[0098] x is an integer equal to or greater than 1;

[0099] y is an integer equal to or greater than 0, with the proviso thatthe sum of x and y is greater than about 4, and

[0100] z is an integer equal to or greater than about 5.

[0101] In more preferred embodiments of this invention, the polyamlineis derived from unsubstituted aniline, i.e., where n is 0 and m is 5(monomer) or 4 (polymer). In general, the number of monomer repeat unitsis at least about 50.

[0102] As described in U.S. Pat. No. 5,232,63 1, the polyaniline isrendered conductive by the presence of an oxidative or acidic species.Acidic species and particularly “functionalized protonic acids” arepreferred in this role. A “functionalized protonic acid” is one in whichthe counter-ion has been functionalized preferably to be compatible withthe other components of this layer. As used herein, a “protonic acid” isan acid that protonates the polyaniline to form a complex with saidpolyaniline.

[0103] In general, functionalized protonic acids for use in theinvention are those of Formulas VI and VII:

A—R  VI

[0104] or

[0105] wherein:

[0106] A is sulfonic acid, selenic acid, phosphoric acid, boric acid ora carboxylic acid group; or hydrogen sulfate, hydrogen selenate,hydrogen phosphate;

[0107] n is an integer from 1 to 5;

[0108] R is alkyl, alkenyl, alkoxy, alkanoyl, alkylthio, alkylthioalkyl,having from 1 to about 20 carbon atoms; or alkylaryl, arylalkyl,alkylsulfinyl, alkoxyalkyl, alkylsulfonyl, alkoxycarbonyl, carboxylicacid, where the alkyl or alkoxy has from 0 to about 20 carbon atoms; oralkyl having from 3 to about 20 carbon atoms substituted with one ormore sulfonic acid, carboxylic acid, halogen, nitro, cyano, diazo, orepoxy moieties; or a substituted or unsubstituted 3, 4, 5, 6 or 7membered aromatic or alicyclic carbon ring, which ring may include oneor more divalent heteroatoms of nitrogen, sulfur, sulfinyl, sulfonyl oroxygen such as thiophenyl, pyrolyl, furanyl, pyridinyl.

[0109] In addition to these monomeric acid forms, R can be a polymericbackbone from which depend a plurality of acid functions “A.” Examplesof polymeric acids include sulfonated polystyrene, sulfonatedpolyethylene and the like. In these cases the polymer backbone can beselected either to enhance solubility in nonpolar substrates or besoluble in more highly polar substrates in which materials such aspolymers, polyacrylic acid or poly(vinylsulfonate), or the like, can beused.

[0110] R′ is the same or different at each occurrence and is alkyl,alkenyl, alkoxy, cycloalkyl, cycloalkenyl, alkanoyl, alkylthio, aryloxy,alkylthioalkyl, alkylaryl, arylalkyl, alkylsulfinyl, alkoxyalkyl,alkylsulfonyl, aryl, arylthio, arylsuldmyl, alkoxycarbonyl,arylsulfonyl, carboxylic acid, halogen, cyano, or alkyl substituted withone or more sulfonic acid, carboxylic acid, halogen, nitro, cyano, diazoor epoxy moieties; or any two R substituents taken together are analkylene or alkenylene group completing a 3, 4, 5, 6 or 7 memberedaromatic or alicyclic carbon ring or multiples thereof, which ring orrings may include one or more divalent heteroatoms of nitrogen, sulfur,sulEmyl, sulfonyl or oxygen. R′ typically has from about 1 to about 20carbons especially 3 to 20 and more especially from about 8 to 20carbons.

[0111] Materials of the above Formulas VI and VII are preferred inwhich:

[0112] A is sulfonic acid, phosphoric acid or carboxylic acid;

[0113] n is an integer from 1 to 3;

[0114] R is alkyl, alkenyl, alkoxy, having from 6 to about 14 carbonatoms; or arylalkyl, where the alkyl or alkyl portion or alkoxy has from4 to about 14 carbon atoms; or alkyl having from 6 to about 14 carbonatoms substituted with one or more, carboxylic acid, halogen, diazo, orepoxy moieties;

[0115] R′ is the same or different at each occurrence and is alkyl,alkoxy, alkylsulfonyl, having from 4 to 14 carbon atoms, or alkylsubstituted with one or more halogen moieties again with from 4 to 14carbons in the alkyl.

[0116] Among the particularly preferred embodiments, most preferred foruse in the practice of this invention are functionalized protonic acidsof the above Formulas VI and VII in which:

[0117] A is sulfonic acid;

[0118] n is the integer 1 or 2;

[0119] R is alkyl or alkoxy, having from 6 to about 14 carbon atoms; oralkyl having from 6 to about 14 carbon atoms substituted with one ormore halogen moieties;

[0120] R′ is alkyl or alkoxy, having from 4 to 14, especially 12 carbonatoms, or alkyl substituted with one or more halogen, moieties.

[0121] Preferred functionalized protonic acids are organic sulfonicacids such as dodecylbenzene sulfonic acid and more preferablypoly(2-acrylamido-2-methyl- 1-propanesulfonic acid) (“PAAMPSA”).

[0122] The amount of functionalized protonic acid employed can varydepending on the degree of conductivity required. In general, sufficientfunctionalized protonic acid is added to the polyaniline-containingadmixture to form a conducting material. Usually the amount offunctionalized protonic acid employed is at least sufficient to give aconductive polymer (either in solution or in solid form).

[0123] The polyaniline can be conveniently used in the practice of thisinvention in any of its physical forms. Illustrative of useful forms arethose described in Green, A. G., and Woodhead, A. E., J. Chem. Soc.,101, 1117 (1912) and Kobay.ashi, et al., J. Electroanl. Chem., 177,281-91 (1984), which are hereby incorporated by reference. Forunsubstituted polyaniline, useful forms include leucoemeraldine,protoemeraldine, emeraldine, nigraniline and tolu-protoemeraldine forms,with the emeraldine form being preferred.

[0124] Copending PCT Patent Application No. PCT/US00/32545 of Cao, Y.and Zhang, C. discloses the formation of low conductivity blends ofconjugated polymers with non-conductive polymers and is incorporatedherein by reference.

[0125] The particular bulk polymer or polymers added to the conjugatedpolymer can vary. The selection of materials can be based upon thenature of the conductive polymer, the method used to blend the polymersand the method used to deposit the layer in the device.

[0126] The materials can be blended by dispersing one polymer in theother, either as a dispersion of small particles or as a solution of onepolymer in the otehr. The polymer are typically admixed in a fluid phaseand the layer is typically laid out of a fluid phase.

[0127] We have had our best results using water-soluble orwater-dispensable conjugated polymers together with water-soluble orwater-dispensable bulk polymers. In this case, the blend can be formedby dissolving or dispersing the two polymers in water and casting alayer from the solution or dispersion.

[0128] Organic solvents can be used with organic-soluble or organicdispensable conjugated polymers and bulk polymers. In addition, blendscan be formed using melts of the two polymers or by using a liquidprepolymer or monomer form of the bulk polymer which is subsequentlypolymerized or cured into the desired final material.

[0129] In those presently preferred cases where the PANI iswater-soluble or water dispersable and it is desired to cast the PANIlayer from an aqueous solution, the bulk polymer should be water solubleor water dispersible. In such cases, it is selected from, for examplepolyacrylamides (PAM), poly(acrylic acid) (PAA) poly(vinyl pyrrolidone)(PVPd), acrylamide copolymers, cellulose derivatives, carboxyvinylpolymer, poly(ethylene glycols), poly(ethylene oxide) (PEO), poly(vinylalcohol) (PVA), poly(vinyl methyl ether), polyamines, polyimines,polyvinylpyridines, polysaccharides, end polyurethane dispersions.

[0130] In the case where it is desired to cast the layer from anon-aqueous solution or dispersion the bulk polymer may be selectedfrom, for example liquefiable polyethylenes, isotactic polypropylene,polystyrene, poly(vinylalcohol), poly(ethylvinylacetate),polybutadienes, polyisoprenes, ethylenevinylene-copolymers,ethylene-propylene copolymers, poly(ethyleneterephthalate),poly(butyleneterephthalate) and nylons such as nylon 12, nylon 8, nylon6, nylon 6.6 and the like, polyester materials, polyamides such aspolyacrylamides and the like.

[0131] In those cases where one polymer is being dispersed in the other,the common solubility of the various polymers may not be required.

[0132] The relative proportions of the polyaniline and bulk polymer orprepolymer can vary. For each part of polyaniline there can be from 0 toas much as 20 parts by weight of bulk polymer or prepolymer with 0.5 to10 and especially 1 to 4 parts of bulk material being present for eachpart of PANI.

[0133] Solvents for the materials used to cast this layer are selectedto compliment the properties of the polymers.

[0134] In the preferred systems, the PANI and bulk polymer are bothwater-soluble or water-dispersible and the solvent system is an aqueoussolvent system such as water or a mixture of water with one or morepolar organic materials such as lower oxyhydrocarbons for example loweralcohols, ketones and esters.

[0135] These materials include, without limitation, water mixed withmethanol, ethanol, isopropanol, acetone methyl ethyl ketone and thelike.

[0136] If desired, but generally not preferred, a solvent system ofpolar organic liquids could be used.

[0137] In the case of conducting polymers such as PANI and bulk polymerswhich are not water-soluble or water-dispersible, nonpolar solvents aremost commonly used.

[0138] Illustrative of useful common nonpolar solvents are the followingmaterials: substituted or unsubstituted aromatic hydrocarbons such asbenzene, toluene, p-xylene, m-xylene, naphthalene, ethylbenzene,styrene, aniline and the like; higher alkanes such as pentane, hexane,heptane, octane, nonane, decane and the like; cyclic alkanes such asdecahydronaphthalene; halogenated alkanes such as chloroform, bromoform,dichloromethane and the like; halogenated aromatic hydrocarbons such aschlorobenzene, o-dichlorobenzene, m-dichlorobenzene, p-dichlorobenzeneand the like; higher alcohols such as 2-butanol, 1-butanol, hexanol,pentanol, decanol, 2-methyl-1-propanol and the like; higher ketones suchas hexanone, butanone, pentanone and the like; heterocyclics such asmorpholine; perfluorinated hydrocarbons such as perfluorodecaline,perfluorobenzene and the like.

[0139] The thickness of the second layer 112 will be chosen with theproperties of the diode in mind. In those situations where the compositeanode is to be transparent, it is generally preferable to have the layerof PANI as thin as practically possible bearing in mind the failureproblem noted in FIG. 1. Typical thicknesses range from about 100 Å toabout 5000 Å. When transparency is desired, thicknesses of from about100 Å to about 3000 Å are preferred and especially about 2000 Å.

[0140] Where the second layer 112 comprises a PANI(ES) blend and a filmthickness of 200 nm or greater, the electrical resistivity of the secondlayer should be greater than or equal to 10⁴ ohm-cm to avoid cross talkand inter-pixel current leakage. Values in excess of 10⁵ ohm-cm arepreferred. Even at 10⁵ ohm-cm, there is some residual current leakageand consequently some reduction in device efficiency. Thus, values ofapproximately from 10⁵ to 10⁸ ohm-cm are even more preferred. Valuesgreater than 10⁹ ohm-cm will lead to a significant voltage drop acrossthe injection/buffer layer and therefore should be avoided.

[0141] The High Conductivity Third Layer (114)

[0142] The material for the third layer 114 should be chosen to matchthe energy level of the photoactive layer 102, or to improve holeinjection/transport of the multilayer anode 104, or to improve theinterfacial properties of the interface between the multilayer anode 104and photoactive layer 102.

[0143] The third component of the hole-injecting electrode is a verythin layer of a highly conductive organic polymer having a resistancethat is lower than the resistance of the material of the second layer112 and higher than the first layer 110. A representative conductiveorganic polymer include pure PANI in its highly conductive forms, thepolypyrroles and preferably polythiophenes such as PEDT, and any of theother organic materials described in the previous section for the secondlayer 112.

[0144] The material from which this layer (114) is formed should have abulk conductivity with is from about five times to about 10⁶ times asgreat as the bulk conductivity of the second layer (112) is formed.Similarly the bulk resistivity should be from five to 10⁶ times lower.Where transparency of the multilayer anode 104 is desired and the layercomprises PEDT, this third layer is typically very thin, often so thinas to likely not be a completely continuous layer. The thickness shouldbe in the range of from about 5 Å to about 500 Å with thicknesses in therange of 10 Å to 50 Å generally being preferred.

[0145] The addition of the high conductivity third layer (114) to secondlayer (112) yields a multilayer structure has a higher conductance thanis observed with the second layer alone. The ratio of conductance of thebilayer (112 and 114) structure to the conductance of second layer 112alone should range from about 1.25 to 20 with ratios of 1.5 to 15 andespecially 2 to 10 being preferred.

[0146] The Cathode (106)

[0147] Suitable materials for use as cathode materials are any metal ornonmetal having a lower work function than the first electrical contactlayer (in this case, an anode). Materials for the cathode layer 106 (inthis case the second electrical contact) can be selected from alkalimetals of Group I (e.g., Li, Cs), the Group 2 (alkaline earth)metals—commonly calcium, barium, strontium, the Group 12 metals, therare earths—commonly ytterbium, the lanthanides, and the actinides.Materials such as aluminum, indium and copper, silver, combinationsthereof and combinations with calcium and/or barium, Li, magnesium, LiFcan be used. Alloys of low work function metals, such as for examplealloys of magnesium in silver and alloys of lithium in aluminum, arealso useful.

[0148] The thickness of the electron-injecting cathode layer ranges fromless than 15 Å to as much as 5,000 Å. This cathode layer 106 can bepatterned to give a pixellated array or it can be continuous andoverlaid with a layer of bulk conductor such as silver, copper orpreferably aluminum which is, itself, patterned.

[0149] The cathode layer may additionally include a second layer of asecond metal added to give mechanical strength and durability.

[0150] The Substrate (108)

[0151] In most embodiments, the diodes are prepared on a substrate.Typically the substrate should be nonconducting. In those embodiments inwhich light passes through it, it is transparent. It can be a rigidmaterial such as a rigid plastic including rigid acrylates, carbonates,and the like, rigid inorganic oxides such as glass, quartz, sapphire,and the like. It can also be a flexible transparent organic polymer suchas polyester—for example poly(ethyleneterephthalate), flexiblepolycarbonate, poly (methyl methacrylate), poly(styrene) and the like.

[0152] The thickness of this substrate is not critical.

[0153] Contact Pads (80, 82)

[0154] Any contact pads 80, 82 useful to connect the electrode of thedevice 100 to the power source (not shown) can be used, including, forexample, conductive metals such as gold (Au), silver (Ag), nickel (Ni),copper (Cu) or aluminum (Al).

[0155] Preferably, contact pads 80, 82 have a height (not shown)projected beyond the thickness of the high work function electrode lines110 below the total thickness of layer.

[0156] Preferably, the dimensions of layers 102, 110, and 112 are suchthat contacts pads 80 are positioned on a section of the substrate 108not covered by layers 102, 112 and 114. In addition, the dimensions oflayer 106, 102, 110, and 112 are such that the entire length and widthelectrode lines 106 and electrode lines 110 have at least one layer 102,112 intervening between the electrodes 106, 110, while electricalconnection can be made between electrode 106 and contact pads 80.

[0157] Other Optional Layers

[0158] An optional layer including an electron injection/transportmaterial may be provided between the photoactive layer 102 and thecathode 106. This optional layer can function both to facilitateelectron injection/transport, and also serve as a buffer layer orconfinement layer to prevent quenching reactions at layer interfaces.Preferably, this layer promotes electron mobility and reduces quenchingreactions. Examples of electron transport materials for optional layer140 include metal chelated oxinoid compounds, such astris(8-hydroxyquinolato)aluminum (Alq₃); phenanthroline-based compounds,such as 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (DDPA) or4,7-diphenyl-1,10-phenanthroline (DPA), and azole compounds such as2-(4-biphenylyl)-5-(4-t-butylphenyl)-1,3,4-oxadiazole (PBD) and3-(4-biphenylyl)-4-phenyl-5-(4-t-butylphenyl)-1,2,4-triazole (TAZ),polymers containing DDPA, DPA, PBD, and TAZ moiety and polymer blendsthereof, polymer blends containing containing DDPA, DPA, PBD, and TAZ.Alternatively, some or all of anode layers 110, 112, 114, thephotoactive layer 102, and cathode layer 106, may be surface treated toincrease charge carrier transport efficiency. The choice of materialsfor each of the component layers is preferably determined by balancingthe goals of providing a device with high device efficiency.

[0159] Fabrication Techniques

[0160] The various elements of the devices of the present invention maybe fabricated by any of the techniques well known in the art, such assolution casting, screen printing, web coating, ink jet printing,sputtering, evaporation, precursor polymer processing, melt-processing,and the like, or any combination thereof.

[0161] In the most common approach, the diodes are built up bysequential deposit of layers upon a substrate. In a representativepreparation, the conductive first layer 110 of the composite electrode104 is laid down first. This layer is commonly deposited by vacuumsputtering (RF or Magnetron), electron beam evaporation, thermal vapordeposition, chemical deposition or the like methods commonly used toform inorganic layers.

[0162] Next, the low conductivity second layer 112 is laid down. Thislayer is usually most conveniently deposited as a layer from solution byspin casting or like technique. In those preferred cases where the layeris formed from water-soluble or water-dispersible material water isgenerally used as the spin-casting medium. In cases where a non-aqueoussolvent is called for are used such as toluene, xylenes, styrene,aniline, decahydronaphthalene, chloroform, dichloromethane,chlorobenzenes and morpholine. This layer can be heat-treated asdescribed in commonly filed U.S. provisional patent application No.60/212,934.

[0163] Next, the higher conductivity layer 114 is deposited. Again, thisis typically done from solution with the solvent selected as describedwith reference to the deposit of layer 112.

[0164] Next, the photoactive layer 102 of conjugated polymer isdeposited. The conjugated polymer can be deposited or cast directly fromsolution. The solvent employed is one which will dissolve the polymerand not interfere with its subsequent deposition.

[0165] Typically, organic solvents are used. These can includehalohydrocarbons such as methylene chloride, chloroform, and carbontetrachloride, aromatic hydrocarbons such as xylene, benzene, toluene,other hydrocarbons such as decaline, and the like. Mixed solvents can beused, as well. Polar solvents such as water, acetone, acids and the likemay be suitable. These are merely a representative exemplification andthe solvent can be selected broadly from materials meeting the criteriaset forth above.

[0166] When depositing various polymers on a substrate, the solution canbe relatively dilute, such as from 0.1 to 20% w in concentration,especially 0.2 to 5% w. Film thicknesses of 500-4000 and especially1000-2000 Å are typically used.

[0167] Finally the low work function electron-injecting contact isadded. This contact is typically vacuum evaporated onto the top surfaceof the active polymer layer.

[0168] These steps can be altered and even reversed if an “upside down”diode is desired.

[0169] It will also be appreciated that the structures just describedand their fabrication can be altered to include other layers forphysical strength and protection, to alter the color of the lightemission or sensitivity of the diodes or the like. It will further beappreciated that the present invention is further useful in organicelectronic devices including the multilayer anode of the presentinvention do not contain a photoactive layer, such as transistors,capacitors, resistors, chemoresistive sensors (gas/vapor sensitiveelectronic noses, chemical and biosensors), writing sensors, andelectrochromic devices (smart window).

[0170] The invention will be further described by the following Exampleswhich are presented to illustrate the invention but not to limit itsscope.

EXAMPLE 1

[0171] PANI(ES) was prepared according to the following reference (Y.Cao, et al, Polymer, 30 (1989) 2307). The emeraldine salt (ES) form wasverified by the typical green color. HCl in this reference was replacedby poly(2-acrylamido-2-methyl-1-propanesulfonic acid (PAAMPSA)(Aldrich). First, 30.5 g (0.022 mole) of 15% PAAMPSA in water (Aldrich )was diluted to 2.3% by adding 170 ml water. While stirring, 2.2 g(0.022M) aniline was added into the PAAMPSA solution. Then, 2.01 g(0.0088M) of ammonium persulfate in 10 ml water was added slowly intothe aniline/PAAMPSA solution under vigorous stirring. The reactionmixture was stirred for 24 hours at room temperature. To precipitate theproduct, PANI(ES), 1000 ml of acetone was added into reaction mixture.Most of acetone/water was decanted and then the PANI(ES) precipitate wasfiltered. The resulting gum-like product was washed several times withacetone and dried at 40° C. under dynamic vacuum for 24 hours.

[0172] This Example demonstrates the direct synthesis of PANI(ES).

EXAMPLE 2

[0173] Four grams (4.0 g) of the PANI(ES) powder prepared in Example 1was mixed with 400 g of deionized water in a plastic bottle. The mixturewas rotated at room temperature for 48 hours. The solutions/dispersionswere then filtered through 1 μm polypropylene filters. Differentconcentrations of PANI(ES) in water are routinely prepared by changingthe quantity of PANI(ES) mixed into the water.

[0174] This Example demonstrates that PANI(ES) can bedissolved/dispersed in water and subsequently filtered through a 1 μmfilter.

EXAMPLE 3

[0175] A poly(ethylenedioxythiophene), PEDT (Baytron P. special grade,commercially available from Bayer), solution was diluted with an equalamount deionized water. The solution was stirred at room temperatureovernight. The PEDT content of the solution was 0.8%. PEDT solutionswere also prepared in which the content of PEDT was 0.4, 0.2 and 0.16%,respectively. All these solutions can be filtered through a 0.231 μmfilter.

EXAMPLE 4

[0176] Thirty grams (30 g.) of a PANI(ES)solution as prepared in Example2 was mixed with 7 g of deionized water and 0.6 g of poly (acrylamide)(PAM)(M.W. 5,000,000-6,000,000, Polysciences) under stirring at roomtemperature for 4-5 days. The weight ratio of PANI(ES) to PAM in theblend solution is 1:2. Blend solutions were also prepared in which theweight ratio of PANI(ES) to PAM was 1:1, 1:1.5, 1:2.5, 1:3, 1:4, 1:5,1:6 and 1:9, respectively.

EXAMPLE 5

[0177] Glass substrates were prepared with patterned ITO electrodes.Using the PANI, PEDT and PANI blend solutions as prepared in Examples 2,3 and 4, layers were spin-cast on top of the patterned substrates andthereafter, baked at 90° C. in a vacuum oven for 0.5 hour. The filmswere then treated at 200° C. in a dry box for 30 minutes. The resistancebetween ITO electrodes was measured using a high resistanceelectrometer. Thickness of the film was measured by using a Dec-Tacsurface profiler (Alpha-Step 500 Surface Profiler, Tencor Instruments).Table 1 compares the conductivity and thickness of PANI(ES),PANI(ES)-PAMblend and PEDT films. As can be seen from Table, the conductivity ofPANI(ES) and PEDT is 10-4 and 10-3 S/cm respectively. Both values aretoo high for use in pixellated displays. The high temperature treatedPANI(ES)-PAM blend has ideal conductivity and thickness for thesematerials to be used in pixellated displays.

[0178] This Example demonstrates that a high temperature-treatedPANI(ES) blend has ideal conductivity and thickness for use inpixellated displays; i.e. sufficiently low that interpixel currentleakage can be limited without need for patterning the PANI(ES) blendfilm. TABLE 1 Bulk conductivity of PANI(ES), PANI(ES)-PAM blend and PEDTThickness Conductivity Blend Baking Condition (Å) (S/cm) PANi —  426 5.1× 10⁻⁴ PEDT — 1221 1.8 × 10⁻³ PANi-PAM (1:2) 200° C./30 min 2195 7.4 ×10-7

EXAMPLE 6

[0179] Light emitting diodes were fabricated using solublepoly(1,4-phenylenevinylene) copolymer (C-PPV) (H. Becker, H. Spreitzer,W. Kreduer, E. Kluge, H. Schenk, I.D. Parker and Y. Cao, Adv. Mater. 12,42 (2000) as the active semiconducting, luminescent polymer; thethickness of the C-PPV films were 700-900 Å. C-PPV emits yellow-greenlight with emission peak at ˜560 nm. Indium/tin oxide was used as theanode contact layer. A layer of PANI, PEDT or PANI-PAM blend was thenapplied using the solutions prepared in Examples 2, 3 and 4. Theselayers were spin-cast on top of the patterned substrates. The layerswere baked at 90° C. in a vacuum oven for 30 minutes, then treated at200° C. in dry box for 30 minutes. The active layer and a metal cathodewere applied. The device architecture was ITO/Polyanilineblend/C-PPV/metal. Devices were fabricated using both ITO on glass(Applied ITO/glass) and ITO on plastic, polyethylene teraphthalate, PET,as the substrate (Courtauld's ITO/PET); in both cases, ITO/Polyanilineblend bilayer was the anode and the hole-injecting contact. Devices weremade with a layer of either Ca or Ba as the cathode. The metal cathodefilm was fabricated on top of the C-PPV layer using vacuum vapordeposition at pressures below 1×10⁻⁶ Torr yielding an active layer witharea of 3 cm². The deposition was monitored with a STM-100thickness/rate meter (Sycon Instruments, Inc.). 2,000-5,000 Å ofaluminum was deposited on top of the 15 Å barium layer. For each of thedevices, the current vs. voltage curve, the light vs. voltage curve, andthe quantum efficiency were measured. The measured operating voltage andefficiencies of the devices with different blend layer are summarized inthe Table 2. As can be seen from the data, the lowest operating voltageand highest light output were achieved from the device with the PEDTlayer.

[0180] This Example demonstrates that highest performance polymer LEDscan be fabricated using PEDT as a hole injection (buffer) layer. TABLE 2Performance of devices fabricated with PANI(ES), PANI(ES)-PAM blend andPEDT Device Performance at 8.3 mA/cm² Blend Baking Condition V cd/A Lm/WPANi — 4.7 7.4 49 PEDT — 4.5 7.7 5.2 PANi-PAM (1:2) 200° C./30 min 6.67.2 3.6

EXAMPLE 7

[0181] Devices produced in accord with Example 6 were encapsulated usinga cover glass sandwiched by UV curable epoxy. The encapsulated deviceswere run at a constant current of 3.3 ma/cm² in an oven at a temperatureof 70° C. The total current through the devices was 10 mA with luminanceof approx. 200 cd/cm². Table 3 and FIG. 3 shows the light output andvoltage increase during operation at 70° C. The light output 300-1,302-1, 304-1 for devices 300, 302 and 304 respectively are shown indashed lines in FIG. 3. The voltage output 300-2, 302-2, 304-2 fordevices 300, 302 and 304 respectively are shown in solid lines in FIG.3.

[0182] In contrast to devices with PANI(ES) and PANI(ES)-PAM blend asanode, which degrade within 160-190 hours of stress at 70° C., the halflife of the devices with the PEDT layer reaches 300 hours with a verylow voltage increase (4.3 mV/hour). It is almost twice longer than thedevice with PANI(ES)-PAM blend. However, PEDT layers alone do not haveresistance sufficiently high to avoid inter-pixel current leakage and isnot suitable for use in pixellated displays. From Ahrennius plots of theluminance decay and voltage increase data collected at 50, 70 and 85°C., the temperature acceleration factor was estimated to be ca. 25 at70° C. Thus, the extrapolated stress life at room temperature wasdetermined to be approximately 7,500 hours for devices with the PEDTlayer.

[0183] This Example demonstrates that longest lifetimes can be obtainedfor polymer LEDS fabricated with PEDT layers. However, these layers donot have resistance sufficiently high to avoid inter-pixel currentleakage. TABLE 3 Stress life of LED devices fabricated with PANI(ES),PANI(ES)-PAM blend and PEDT Stress Life Baking at 70° C. at 3.3 mA/cm²Ref. No. Blend Condition mV/h cd/m²* t_(½)(h) 300 PANi — 7.4 185 186 302PEDT — 4.3 185 300 304 PANi-PAM (1:2) 200° C./30 11.3 171 168 min

EXAMPLE 8

[0184] The resistance measurements of Example 5 were repeated, but thePANI(ES) layer was spin-cast from the blend solutions prepared inExamples 4 at 1400 rpm. The weight ratio of PANI(ES) to PAM in the blendsolution is 1:2. The film was baked at 200° C. for 30 minutes in dry boxafter dried in 90° C. vacuum oven for 0.5 hour. The thin PEDT film wasspinning cast on the top of the PANI blend layer from the solutionprepared in Example 3. The thickness of the PEDT layer is ranged from970 Å to ˜10 Å. The resistance between ITO electrodes was measured usinga high resistance electrometer. Thickness of the film was measured byusing a Dec-Tac surface profiler (Alpha-Step 500 Surface Profiler,Tencor Instruments). Table 4 shows the surface resistance ofPANI(ES)-blend/PEDT double layer films with different PEDT thickness. Ascan be seen from Table, the surface resistance of thePANI(ES)-blend/PEDT double layer can be controlled over a wide range,from 10⁷ to 10⁹ ohm/sq by adjusting the thickness of PEDT layer. Whilethe thickness of PEDT decrease to below 50 Å, the conductivity of thedouble layer is below 10⁸ ohm/sq, which is ideal for use in pixellateddisplays.

[0185] This Example demonstrates that PANI(ES)-blend/PEDT double layerfilms can be prepared with conductivity less than 10⁸ ohm/sq. TABLE 4Surface Resistance of PANI(ES)-PAM/PEDT double layer with different PEDTthickness PEDT Double Solution Spinning PEDT Layer Surface ConcentrationRate Thickness Thickness Resistance (%) (rpm) (Å) (Å) (ohm/sq) 1.6 800970 2768 5.8 × 10⁷ 0.8 3000 192 1788 4.0 × 10⁸ 0.8 6000 90 1962 5.8 ×10⁸ 0.4 6000 ˜50 2694 1.4 × 10⁹ 0.2 3000 ˜40 2025 5.3 × 10⁹ 0.2 6000 ˜201640 6.1 × 10⁹ 0.16 4000 ˜10 2045 5.8 × 10⁹

EXAMPLE 9

[0186] The device measurements summarized in Example 6 were repeated,but the PANI blend layer was replaced with PANI(ES)-blend/PEDT doublelayers prepared as in Examples 8. Table 5 shows the device performanceof LEDs fabricated from polyblend films with various double layers.Devices fabricated with PANI blend/PEDT double layers exhibit the sameoperating voltage and light efficiency as devices made with PEDT layers.

[0187] This Example demonstrates that a PANI blend/PEDT double layer canbe used to fabricate polymer LEDs with the same low operating voltageand high efficiency as devices made with a PEDT layer. TABLE 5Performance of devices fabricated with PANI(ES)-PAM/PEDT double layerwith different PEDT thickness PEDT Solution Spinning PEDT DeviceConcentration Rate Thickness Performance at 8.3 mA/cm² (%) (rpm) (Å) Vcd/A Lm/W 1.6 800 970 5.3 6.9 4.1 0.8 3000 192 4.3 7.2 5.2 0.8 6000 904.2 7.6 5.6 0.4 6000 ˜50 4.2 7.6 8.2 0.2 3000 ˜40 4.9 8.0 5.1 0.2 6000˜20 4.7 8.3 5.5 0.16 4000 ˜10 5.0 8.1 5.1

EXAMPLE 10

[0188] The stress measurements summarized in Example 7 were repeated,but the PANI blend layer (incorporated in device 300 in Table 3) wasreplaced by PANI blend/PEDT double layers prepared as in Examples 8.Table 6 and FIG. 4 show the stress life of devices fabricated with aPANI blend/PEDT double layer. In FIG. 4, the light output 302-1, 304-1,402-1, 404-1, and 406-1 for devices 302 and 304 as shown in Table 3 anddevices 402, 404 and 460 as shown in Table 6, respectively, are shown indashed lines. The voltage output 302-2, 304-2, 402-2, 404-2, and 406-2for devices 302 and 304 as shown in Table 3 and devices 402, 404 and 460as shown in Table 6, respectively, are shown in solid lines.

[0189] As can be seen from the data, the voltage increase rate of thedouble layer device with an ˜10 Å to 20 Å layer of PEDT is slightlylower than that of device made from PEDT. The half-life time of thedouble layer device is even slightly longer than that of the PEDTdevice.

[0190] This Example demonstrates that the PANI blend/PEDT double layercan combine the high resistance of PANI blend and long life stresslifetime of PEDTin one device. TABLE 6 Stress life of LED devicesfabricated with PANI(ES)-PAM/PEDT double layer with different PEDTthickness FIG. PEDT 4 Solution Spinning PEDT Stress Life at 70° C. RefConcentration Rate Thickness at 8.3 mA/cm² No. (%) (rpm) (Å) MV/h cd/m²*t_(½)(h) 1.6 800 970 9.2 194 221 0.8 3000 192 5.8 144 300 402 0.8 600090 3.8 189 319 404 0.4 6000 ˜50 3.4 171 350 0.2 3000 ˜40 4.7 189 303 4060.2 6000 ˜20 4.2 190 328 0.16 4000 ˜10 3.8 190 330

EXAMPLE 11

[0191] The resistance measurements of Example 5 were repeated, but thePANI(ES) layer was spin-cast from the blend solutions prepared inExamples 4. The weight ratio of PANI(ES) to PAM in the blend solution is1:1.5, 1:2, 1:3,1:4 1:5 and 1:6. The film was baked at 200° C. for 30minutes in dry box after dried in 90° C. vacuum oven for 0.5 hour. Thethin PEDT film was spinning cast on the top of the PANI blend layersfrom the solution prepared in Example 3. The concentration of PEDTsolution is 0.16% and the spinning rate is 4000 rpm. The thickness ofthe PEDT layer is ˜10 Å. The resistance between ITO electrodes wasmeasured using a high resistance electrometer. Thickness of the film wasmeasured by using a Dec-Tac surface profiler (Alpha-Step 500 SurfaceProfiler, Tencor Instruments). Table 7 shows the surface resistance ofPANI blend/PEDT double layer films with different PANI(ES) to PAM ratio.As can be seen from the Table, the surface resistance of the PANIblend/PEDT double layer can be controlled over a wide range, from 10⁸ to10¹⁵ ohm/sq by adjusting the weight ratio of PANI(ES)-PAM layer.

[0192] This Example demonstrates that PANI blend/PEDT double layer filmscan be prepared with conductivity less than 10⁸ ohm/sq and even lessthan 10¹³ ohm/sq. TABLE 7 Surface Resistance of PANI(ES)-PAM/PEDT doublelayer with different PANI(ES)-PAM blend Double Layer Surface CompositionThickness Resistance PANI Blend (w:w) (Å) (ohm/sq) PANI-PAM 1:1.5 18226.6 × 10⁸  PANI-PAM 1:2 2078 5.7 × 10⁹  PANI-PAM 1:3 2252 2.1 × 10¹³PANI-PAM 1:4 1621 1.1 × 10¹⁵ PANI-PAM 1:5 1734 9.0 × 10¹⁴ PANI-PAM 1:62422 9.6 × 10¹⁴

EXAMPLE 12

[0193] The device measurements summarized in Example 6 were repeated,but the PANI blend layer was replaced with PANI blend/PEDT doublelayers. Table 8 shows the device performance of LEDs fabricated frompolyblend films with different double layers. When the PANI to PAM ratiowas larger than 1:4, devices fabricated with PANI blend/PEDT doublelayer exhibited the same operating voltage and light efficiency asdevices made with a PEDT layer alone. The lower PANI(ES) to PAM ratiosresult in deterioration of device performance.

[0194] This Example demonstrates that PANI blend/PEDT double layers canbe used to fabricate polymer LEDs with the same low operating voltageand high efficiency as devices made with a PEDT layer alone. TABLE 8Performance of devices fabricated with PANI(IES)-PAM/PEDTdouble layerwith different PANI(ES)-PAM blends Device Performance Composition DoubleLayer at 8.3 mA/cm² PANI Blend (w:w) Thickness (Å) V cd/A Lm/W PANI-PAM1:1.5 1822 6.0 6.4 3.4 PANI-PAM 1:2 2078 5.0 8.1 5.1 PANI-PAM 1:3 22525.8 7.9 4.3 PANI-PAM 1:4 1621 5.8 8.8 4.6 PANI-PAM 1:5 2422 8.0 8.7 3.1PANI-PAM 1:6 2078 8.3 8.2 3.0

EXAMPLE 13

[0195] The stress measurements summarized in Example 7 were repeated,but the PANI(ES)-blend layer was replaced with PANI blend/PEDT doublelayers. Table 9 and FIG. 5 show the stress life of devices fabricatedwith the PANI(ES) blend/PEDT double layers at 80° C. The luminance500-1, 502-1, 504-1, and 506-1 devices 500, 502, 504 and 506respectively are shown in dashed lines in FIG. 3. The voltage output500-2, 502-2, 504-2, and 506-2 for devices 500, 502, 504 and 506respectively are shown in solid lines in FIG. 5. When the PANI to PAMratio is larger than 1:4, the voltage increase rate of the double layerdevice was lower than that of devices made from PEDT. The half-life timeof the double layer device is even longer than that of the PEDT deviceat 80° C.

[0196] This Example demonstrates that the PANI(ES) blend/PEDT doublelayer can combine the high resistance of PANI blend and the long lifestress life time of PEDT in one device. TABLE 9 Stress life of LEDdevices fabricated with PANI(ES)-PAM/PEDT double layers with differentPANI(ES)-PAM blend Ref. No. Composition Double Layer Stress Life at 70°C. at 3.3 ma/cm²: In FIG. 5 PANI Blend (w:w) Thickness (Å) mV/h cd/m²*t_(½)(h) 500 PEDT — — 19.6 217 80 PANI-PAM 1:1.5 1822 19.8 198 108 502PANI-PAM 1:2 2078 15.7 210 123 PANI-PAM 1:3 2252 17.9 180 89 504PANI-PAM 1:4 1621 19.5 229 81 506 PANI-PAM 1:5 2422 67.2 232 61 PANI-PAM1:6 2087 124.8 210 53

What is claimed is:
 1. A multilayer electrode comprising a first layer having a first layer conductivity, a second layer in contact with the first layer, said second layer comprising a conductive organic material having a second layer conductivity, and a third layer in contact with the second layer, said third layer comprising a conductive organic material having a third layer conductivity greater than the second layer conductivity and less than the first layer conductivity.
 2. A pixellated display comprising the multilayer electrode of claim
 1. 3. The multilayer electrode of claim 1, wherein the second layer has a bulk conductivity of from 10⁻⁴ S/cm to 10⁻¹¹ S/cm and wherein the bulk conductivity of the third layer is from about 5 times to about 10⁶ times as great as the conductivity of the second layer.
 4. The multilayer electrode of claim 1, wherein said second layer comprises a blend of conjugated conductive organic polymer with nonconductive polymer.
 5. The multilayer electrode of claim 1, wherein the second layer comprises a blend of PANI with nonconductive polymer.
 6. The multilayer electrode of claim 1, wherein the conductance of the second layer in combination with the third layer is from 1.25 to about 20 times the conductivity of the second layer alone.
 7. The multilayer electrode of claim 1, wherein the first layer comprises indium-tin oxide, the second layer comprises a water-soluble PANI blend, and the third layer comprises a poly(ethylenedioxythiophene).
 8. The array of claim 1 wherein the second layer has a thickness of from about 500 Å to about 5000 Å.
 9. The array of claim 1 wherein the third layer has a thickness of from about 2 Åto about 400 Å.
 10. The array of claim 1 wherein said second layer comprises a mixture of conjugated conductive organic polymer with a nonconductive host polymer.
 11. An electronic device comprising a photoactive layer between a cathode and an anode, wherein the anode is a multilayer anode including a first anode layer comprising high conductivity transparent inorganic contact layer, a second anode layer adjacent to the first anode layer, said second anode layer comprising conjugated conductive organic polymer and having a low conductivity and a third anode layer between said second anode layer and said photoactive layer, said third anode layer comprising a conductive organic polymer and having a higher conductivity resistance than said second anode layer.
 12. The device of claim 11, wherein the cathode comprises a first cathode layer of low work function material and a second layer of electron transport/injection material between the photoactive layer and the first cathode layer, the first anode layer having anode work function and the low work function material having a cathode work function such that the anode work function is higher than the cathode work function.
 13. The device of claim 11, wherein said second layer comprises a blend of conjugated conductive organic polymer with nonconductive polymer.
 14. The device of claim 11, wherein the second layer comprises a blend of PANI with nonconductive polymer.
 15. The device of claim 11, wherein the second layer has a bulk conductivity of from 10⁻⁴ S/cm to 10⁻¹¹ S/cm and wherein the bulk conductivity of the third layer is from about 5 times to about 10⁶ times as great as the conductivity of the second layer.
 16. The device of claim 11 wherein the conductance of the second layer in combination with the third layer is from 1.25 to about 20 times the conductivity of the second layer alone.
 17. The device of claim 11 wherein the photoactive layer comprises a poly(phenylenevinylene)-based polymer, the cathode comprises an alkaline earth metal and the anode comprises a indium-tin oxide first layer, a water-soluble PANI blend second layer and a poly(ethylenedioxythiophene) third layer.
 18. The device of claim 11, wherein the photoactive layer comprises an active material is selected from asanthracene, butadienes, coumarin derivatives, acridine, stilbene derivatives, and combinatios thereof.
 19. The device of claim 11, wherein the photoactive layer a conjugated polymer active material.
 20. An array of polymer emissive diodes comprising an active emissive polymer layer having a first side in contact with a patterned cathode and a second side in contact with a patterned transparent anode, the patterning of said anode and cathode defining an array of emissive diodes, wherein a multilayer anode including a first layer comprising a patterned high conductivity inorganic contact layer, a nonpatterned second layer in contact with said first layer, said second layer comprising conjugated conductive organic polymer and having a high resistance and a nonpatterned transparent third layer in contact with said second layer and with said active emissive polymer layer, said third layer comprising a conductive organic polymer and having a lower resistance than said second layer.
 21. The array of claim 20 wherein said second layer comprises a blend of conjugated conductive organic polymer with nonconductive polymer.
 22. The array of claim 20 wherein said blend is a dispersion of one polymer in the other.
 23. The array of claim 20 wherein said blend is a solution of one polymer in the other.
 24. The array of claim 20 wherein the diode of claim 2 wherein the second layer comprises a blend of PANI with nonconductive polymer.
 25. The array of claim 24 wherein the diode of claim 2 wherein the second layer has a bulk conductivity of from 10⁻⁴ S/cm to 10⁻¹¹ S/cm and wherein the bulk conductivity of the third layer is from about 5 times to about 10⁶ times as great as the conductivity of the second layer.
 26. The array of claim 25 wherein the conductance of the second layer in combination with the third layer is from 1.25 to about 20 times the conductivity of the second layer alone.
 27. The array of claim 20 wherein said patterned high conductivity transparent inorganic contact layer is present on a support.
 28. The array of claim 25 wherein the second layer has a thickness of from about 500 Å to about 5000 Å.
 29. The array of claim 25 wherein the third layer has a thickness of from about 2 Å to about 400 Å.
 30. The array of claim 23 wherein said second layer comprises a mixture of conjugated conductive organic polymer with a nonconductive host polymer. 